A new study revealed that the occurrence of narcolepsy in China is related highly to seasonal patterns, with onset most common in April. Following the 2009-2010 H1N1 pandemic, a significant rise in narcolepsy cases were also observed. However, the findings indicated flu vaccination was unlikely the cause of the rise. The study is now available in Annals of Neurology, a journal of the American Neurological Association and the Child Neurology Society.

Caused by a deficit of hypocretin – a neurotransmitter in the brain that is responsible for communication of biological processes, such as sleep. Narcolepsy is a chronic neurological disorder. An inability to control sleep-wake cycles occurs when brain cells lose hypocretin. Individuals with the disorder experience sudden bouts of sleep at any time, a sudden loss of voluntary muscle tone (cataplexy), vivid dreams or hallucinations, and short periods of total paralysis, according to the National Institutes of Neurological Disorders and Stroke (NINDS).

Medical evidence reveals that narcolepsy-cataplexy affects less than 1% of the world population and 1 in 3,000 Americans have this disorder, estimates NINDS. Investigations reported, following the 2009-2010 H1N1 pandemic, patients who were receiving the Pandermrix vaccine had an increased incidence in narcolepsy and increased risk of narcolepsy. Other research revealed that infection with streptococcus preceded the onset of narcolepsy in Caucasian patients, suggesting upper airway infections may set off the disorder.

The investigation team for the current study, led by Dr. Fang Han from the Beijing University People’s Hospital in China and Dr. Emmanuel Mignot with the Stanford Center for Sleep Sciences and Medicine in Palo Alto, California, conducted a retrospective examination of narcolepsy onset in patients diagnosed between 1998 and 2011 in Beijing. Information was gathered from 629 patients (86% children), who were participants of the Stanford-Beijing University Chinese narcolepsy study cohort, on the month and year of narcolepsy onset. 182 participants who developed narcolepsy after October 2009 provided a vaccination history.

Dr. Han explained,

“Our findings show a seasonal variation in narcolepsy onset in a Chinese population, occurring most frequently in late spring and early summer. Analysis revealed that onset of narcolepsy was least frequent in November and occurred most often in April, with close to a 7-fold increase from lowest point to peak time.”

Year-to-year variations were also researched by the investigators, identifying 173 cases of narcolepsy following the 2009-2010 H1N1 flu pandemic which represented a three fold rise in the disorder. Dr. Mignot noted, “The increase in narcolepsy incidence was unlikely caused by increased vaccination as only 6% of study narcolepsy participants reported receiving a vaccination against H1N1. A five to seven month delay between the seasonal peak in flu and peak in the onset of narcolepsy was also observed.”

He concluded,

“These findings are reminiscent of the encephalitis lethargica epidemic that followed the great Spanish influenza pandemic of 1917-1918. Not only narcolepsy, but also psychosis and Parkinson’s disease may follow winter infections, and further research is needed in the area of autoimmune diseases of the brain.”

Grace Rattue